The present invention relates to a photoconductor for electrophotography (hereinafter referred to as a "photoconductor") for use in electrophotographic apparatuses, such as printers, copying machines, and facsimiles. In particular, the present invention relates to a photoconductor which includes a photoconductive film having a stable layer containing a charge transport agent. The present invention also relates to an electrophotographic apparatus which includes the photoconductor of the present invention, as well as a method of manufacturing such a photoconductor.
Photoconductors retain surface charges in the dark, generate electric charges in response to received light, and transport the generated electric charges in response to the received light. Photoconductors may be classified into monolayered photoconductors, which have a single layer that exhibits all the above described functions, and laminate-type photoconductors, which have one layer for charge generation and a second, separate layer for charge retention in the dark and charge transport in received light.
Conventional photoconductors employ the Carlson method for electrophotographic image formation. Image formation by the Carlson method requires charging the photoconductor in the dark by corona-discharge, forming electrostatic images of the original letters and pictures on the charged surface of the photoconductor, developing the electrostatic images with toner, and copying the developed toner images to the carrier paper. The photoconductor is ready for reuse after discharging, removal of residual toner and optical discharging are completed.
Photoconductive materials used in photoconductors include inorganic materials such as selenium, selenium alloys, zinc oxide, and cadmium sulfide. Photoconductive materials for the photoconductor may also include organic photoconductive materials, such as poly-N-vinylcarbazole, 9,10-anthracenediolpolyester, hydrazone, stilbene, butadiene, benzidine, phthalocyanine compounds, and bisazo compounds. The photoconductive materials are dispersed in a resin binder or deposited by vacuum deposition or by sublimation. Various additives may also be included to improve the electrophotographic properties.
German Patent Specification No. 3 625 766 discloses phosphite compounds as a phosphorus containing additive for preventing photodeterioration in electrophotographic photoconductors. German Patent Specifications No. 2 117 509, No. 2 304 301, No. 2 834 871 and No. 2 944 154, U.S. Pat. No. 3,978,020 and the Japanese Unexamined Laid Open Patent Application No. S62-7725 describe phosphonite stabilizers for resin moldings. The phosphonite compounds have been used mainly to stabilize the resin moldings, which are subject to heat treatments at high temperatures. However, phosphonite compounds have not previously been used as additives to electrophotographic photoconductors.